This focus of these experiments is on the behavior and neurochemical changes of cocaine users during and after a smoked cocaine binge. Specifically, the investigators will examine prolactin (PRL) release following administration of the dopamine (DA) agonist bromocriptine in abstinent male and female cocaine users after various time periods after a cocaine binge. There are two hypotheses: The closer in time to the cocaine binge that bromocriptine is given, the smaller the decrease in PRL levels. An additional interest is to determine how menstrual cycle phase influences cocaine's direct effects. The second hypothesis is that women will be more sensitive to cocaine's subjective effects during the luteal phase than the follicular phase. In addition to non-treatment-seeking cocaine users, a matched group (matched by age, sex, and menstrual cycle phase) of non-cocaine-dependent participants will be recruited. The study will examine prolactin and growth hormone release following the administration of bromocriptine in this group as well, with females studied during the follicular phase of the mentrual cycle. This study will provide data to increase our understanding of the effects of gonadal hormones on cocaine's effects, as well as our understanding of the effects of chronic cocaine exposure on dopaminergic neurons. The goal is to use these data to develop more effective treatments for cocaine abuse.